DVD-Rom difficulty with DVDs

I have a DVD-ROM with WinDVD software. It will let me play VCD discs but won't even recognize a disc being present once I insert an actual DVD. Does anyone have any suggestions of what to do, or if there are any good software. I run Windows XP Pro. Thanks!

It's so weird though. A while back I ripped some DVDs with the same drive in the same PC. After a couple of formats I cannot rip the same or play the same DVDs that I have done in the past. I have tried everything that I did the first time plus some. I never took the rom out or anything. I know, sounds kinda weird, but very flustering!